Milo g



(No Model.)

M. G. KBLLOGG. MULTIPLE SWITGHBOARD.

Patented Oct. 26, 1897.

UNrTnn STATES PATENT OFFICE..

MILO G. KELLOGG,'OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGG S\VITCIIBOARD AND SUPPLY COMPANY, OF SAME PLACE.

MULTIPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent No. 592,333, dated October 26, 1897.

Application filed December 12,1889. Serial No. 333,536. (No model.)

To all whom t may concern:

Bc it known that l, Mino G. KELLOGG, of Chicago,Illinois,temporarily residing at Stuttgart, in the Empire of Germany, have invented certain new and useful Improvements in Multiple Switchboards for Telephone-EXchan ges, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawing, forming a part of this specication.

Myinvention relates to lines which are normally grounded at the central office.

It consists, first, of an improved system of subscribers calling on such lines; secondly, to an improved system of testing such lines, and, thirdly, to an improved night-signal at the central oflice.

In the accompanying drawing, illustrating my invention, the figure shows the apparatus and the circuit connections preferably used therewith.

There are as many boards in the exchange as the number of lines renders necessary, and the line-annunciators are distributed among the operators in such a way as to equalize their work. On each board is a switch for each line. Each switch is preferably in the form of a spring-jack having three contacts, two of which are normally in contact, but disconnected by the insertion of a switch-plug, and the third insulated'from the other two, except for the circuit connections, and so placed as to be conveniently touched by a test plug or device for the purpose of testing. The connections of a subscribers line may be traced from ground G at the subscribers station in parallel through two branches, one containing the telephone 4, the ot-her aI short circuit 6, terminating in a contact 5 normally, or when the telephone is not switched for use in connection with the switch-lever 3, thence in multiple through two other branches, one containing the call-generator 2 and the bells l, and the other being a short circuit 8 around the calling set, terminating in a contact '7, connected with the switch-le ver only while the telephone is switched for use, as shown in line No. l, thence over the line conductor to the pairs of contacts g h in the spring'jacks a and b or a and b', as the case may be, at boards A and B, thence through tcst-contactsj at each board connected together by the test-wire T', contacts p q, annunciator w or cc, as the case may be, to ground at G.

The annunciators w and are each mounted upon a conductingplate f, upon which is mounted a spring-contact q, in electrical connection therewith, so bent as to normally make connection with the contact p, mounted upon, but insulated from, the plate f. The normal connections are shown in line No. 2. When the annunciator drops its flap f, the cam-shaped base of the flap forces the spring q away from the contact p and thus disconnects the test-wire T from the office ground.

Upon' the plate f, but insulated therefrom, is mounted an additional contact r, so placed that when the spring q leaves the contact p it comes into connection with the contact r, so that when the annunciator-iiap falls it closes the circuit through the signal-bell S' and battery Bconnected by multiple connections e and e to the plate o and the contact r, respectively, so that the Hap of an annunciator when it falls performs two functions-m it opens the line connection to ground and it closes a signal bell circuit. This bell-circuit may be open during the day and closed for use at night, or it may be used at all times. There may be one bell for the eX- change, but I prefer to arrange a different bell on cach board, common to the groups of lines at that board, so that a night operator is easilydirected to the proper board when a call is made.

In my application, Serial No. 333,343, filed December ll, 1889, I have described and claimed a system in which there isa distinctive night-signal upon a night-table common to the lines of each board. In this case the board-signal is located at the board itself.

I-Icretofore operators at night have been compelled to hunt over all the annunciators of the exchange to find the line that has sent in a call. In my system the operator is at once directed to the board that has called by the bell ringing at that board.

At each board is a test outfit comprising a battery B' and test receiving instrument S, grounded on one side, and on the other connected to a test plug or device T, adapted to IOO be connected to a test-contact j of a line for testing. .The test-battery and test receiving instrument and the two grounded branches or ends ot', the line-circuit and the apparatus in said circuit are so adjustedto each other that the test'receiving instrument will sound When on testing neither the line is switched at a switchboard nor the annunciator-contacts are open, but not otherwise. To accomplish this result, the line-annunciator is given such a resistance that when the test outfit is in circuit with it and not in circuit with the subscribers outfit in. multiple the test outfit will fail to respond, and theline will indicate busy The subscribers outt isgiven such a resistance that when it is in circuit with the test outfit alone, and the oiice ground G has been cut olf by the calling-annunciator, the test outfit will fail to respond. v

The resistance in the subscriber-s outfit lies vpreferably in the calling and the telephone sets, and the resistance of either set is sufficient to prevent a response from the test outfit ,when the ann unciator-co'ntacts p q are open, but not enough to prevent a response when those contacts are closed. The resistance of the annunciator branch may be in the coil itself or in a separate resistance, or in both, inthe manner well-known to electrical engineers.

The joint resist-ance of the annunciator y is preferably high, so that when in an ad- -as shown at board B, a test outiit (shown at board A, for example) will not respond.

At board B the test'outiit is showny connected to the test-contactj of the spring-jack b. It is thus connected in a test-circuit traced from the grounded test outiit in the order named through test-contactj of spring-jack b', test-Wire T', two branches in multiple, one comprising the normally closed contacts p q, annunciator' a5, grounded at g, the other comprising the normally closed contacts h g, the line conductor, and the grounded subscribers outfit. The test receiving instrument S is shown responding to this test-circuit.

At board A the operators test outfit is shown connected to the test-contactj of jack ci for the purposeoil testing the condition of line No. l. The test-wire T is disconnected from the line conductor at jack yb at board B, where the contacts g h are disconnected from each other by theinsertion of the switchi plug D. The test-wire T is also disconnected ing outfit adapted to connect together two lines for conversation. The apparatus may be variously arranged, but I prefer the arrangement shown, in which two switch-plugs D and D', having contacts n mounted upon insulating material m, are connected through .a flexible cord-circuit d, in which is a looping-in switch Y, adapted to be placed upon pairs of contacts q q', r' r', s' s', and thereby loop into the circuit of the switch-plugs the operator-s telephone set t, the battery or alternating call-generator B2, or the clearingout annunciator fu. The contacts n of the plugs are so arranged that they make connection normally with a conducting base-plate o, grounded at G. Thus when one plug is inserted into a line-jack the circuit of the operators outfit is completed through the contact n of the other plug and the grounded baseplate 0, upon which it rests. iVhen two lines are connected together for conversation, the contacts g of the spring-jacks of those lines are connected together through the operators outfit, and the clearing-out annunciator fu is left in the circuit for the purpose of clearing,r out.

The adjustment of the test system with various resistances and test outfits depends upon the degree of resistance, the size of the battery, the strength of the retractile spring of the test receiving instrument, and the power and number of coils of the magnet of the test receiving instrument. For instance, the resistance of the lines may be about two hundred and fifty ohms each and the resistance of the annunciator magnets may be about two hundred and fifty ohms each. When under such conditions the test-plug T is applied to a oontact-piecej of a line, and neither the line is switched at any board nor the annunciator indicates a call, the battery iindsground both through the switch contactpoints to the subscribers station and through vthe annunciator contact-points and the annunciator-magnets, and the resistance from the plug to such ground will be about one hundred and twenty-five ohms. With an ordinary bell of,say,one hundred ohms and eight or ten cellsy of battery and a suitable retractile spring the bell may be adjusted so as to ring when closed through such a circuit of, say, one hundred and twenty-five ohms resistance, but not to ring when the resistance of the circuit through which it is closedY is increased to, say, two hundred and fifty ohms. When, the test being made as above, the line is switched at any board, (the annunciator not indicating a call,) the circuit to the subscribers ground will be open and the resistance will be that tothe office ground, which is, say, two hundred and fty ohms, and the bell will not ring. When again the test is made IOO IIO

and the annunciator indicates a call, (the line not being switched at any board,) the circuit to the otce ground will be open and the resistance will be that to the subscribers ground, which is, say, two hundred and titty ohms, and the bell will not ring. Vhen again the test is applied and both the line is switched and the annunciator indicates a call, no circuit is established, and the bell will not ring. The operator can therefore know when the bell rings that neither the line is switched nor the annunciator indicates a call, and when it does not ring the bell either the line is switched or the annunciator indicates a call, or both.

The night-bell S may be asingle or continuous stroke bell. If continuous, it may be a vibrating bell operated by any suitable eurrent, or it may be a polarized bell operated by a current of alternating polarity, or under proper conditions by an intermittent current of one polarity. The particular character of the bell is immaterial, as long as it is suiiicient to attract the attention of an operator to the board at which it is located. It is obvious that an annunciator might be substituted for the call, and the noise caused by the dropping of the 'Hap be utilized for attracting the attention of the operator. The Law or any other system of calling may be substituted for that shown, so arranged as to perform the same functions.

In ordinary systems the subscribers generator, when actuated for a call, is apt to cause induction on neighboring lines and thus interfere with conversation on those lines. My system obviates this difficulty, for the callingannunciator opens the office-ground connection of the line when it indicates a call, and the subscribers generator is left on open circuit. The subscriber is also informed that his call is indicated by his bell, which stops ringing when the line-circuit is thus opened. Although the system has been described as a grounded system, it is evident that a metallic conductor might be substituted therefor, or the circuits may be metallic, and the individual return-conductors of all the circuits be joined together and connected to the apparatus, shown as grounded, or some lines may be metallic and some grounded, and the metallic returns of the metallic circuits connected to ground at the central office.

Various other modifications may be made without departing from my invention.

rl`he switch Y of the connecting apparatus should normally rest upon the pair of contact-points s s. The connection in multiple of the operators telephone set and the calling-generator B2 to the other sets of connecting apparatus is well understood by telephoneengineers.

At board A is shown the night-call S' and battery B3, operated by the annunciators located at that board. These annunciators are not shown.

I claim as my invention and desire to secure by Letters Patentl. In a multiple -switchboard exchange, a test -circuit comprising three parallel branches, one temporarily closed branch containing a test receiving instrument, and each of the other two branches normally closed through contacts opened by switchboard apparatus when in use, said test receiving instrument giving one indication while the two branches are closed, and giving a second indication While they are open, and a test-battery in said test-circuit.

2. In a multiple-switchboard exchange, a test circuit comprising three parallel branches, one temporarily closed branch containing a test receiving instrument and bat-,

tery, and each of the other two branches normally closed but opened by switchboard apparatus while in use, resistances in each of said other two branches, said test receiving instrument and battery being so adjusted to each other and to said resistances as to give one indication while the two branches are closed, and a dilterentindication while either or both of said branches are open.

3. In a multiple-switchboard exchange, in the ordernamed, a grounded subscribers circuit, normally closed switchboard-contacts open While the line is switched for use, testcontacts, call-contacts, normally closed but open during a call, and a ground connection; in combination with a grounded test outfit adapted to be connected to a test-contact and give one indication while said switchboard and call contacts vare closed, and a diierent indication While said contacts are open.

et. In a multiple-switchboard exchange, in the order named, a grounded subscribers outt containing a resistance, normally closed switchboard-contacts open while the line is switched for use, test-contacts, and a call-circuit and resistance grounded through normally closed contacts open during a call; in combination with a grounded test outfit adapted to be connected to a test-contact for testing so adjusted to said resistances as to give one indication while said contacts are closed and a different indication while either the call-contacts or the switchboard-contacts or both are open.

5. In a multiple-switchboard exchange, in the order named, a grounded subscribers line containing a resistance, pairs of normally closed switchbcard-contacts, one pair at each board opened while the line is switched for use, test-contacts, one at each board, an annunciator-circuit containing a resistance,normally closed contacts open during a call, and a ground connection; in combination with grounded test receiving instruments, one at each board, adapted te be connected to a testcontaet for testing, and test-batteries, said batteries and test receiving instruments being so adjusted to said resistances as to respond while on testing, neither the switchboard nor the annunciator contacts are open, but not otherwise.

G. In a multiple-switchboard exchange, in

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the order named, a grounded subseribers line containing a resistance, pairs of normally closed switchboard-contacts, one pair at each board opened while the line is switched for use, test-contaets, one at each board, an an# nuneiator-circuit containing at resistance and normally closed contacts open during L call, and a ground Connection; in combination with grounded test receiving-instrurnents, one at each board, adapted to be connected to a testeontztet for testing, and test-batteries, said batteries and test receiving instruments being so adjusted to said resistanees as to respond While on testing, neither the switchboard nor the annunciator contacts are open, but not otherwise, and :t switch-plug adapted to open a pair of said switchboard-contacts.

MILO G. KELLOGG.

\Vitnesses:

FRANCES D. KELLOGG, MARGARETHA RIEHL. 

